Dendritic cell immunoreceptor 1 alters neutrophil responses in the development of experimental colitis

The C-type lectin DCIR contributes to the immune response and pathogenesis of colorectal cancer

Development and progression of malignancies are accompanied and influenced by alterations in the surrounding immune microenvironment. Understanding the cellular and molecular interactions between immune cells and cancer cells has not only provided important fundamental insights into the disease, but has also led to the development of new immunotherapies. The C-type lectin Dendritic Cell ImmunoReceptor (DCIR) is primarily expressed by myeloid cells and is an important regulator of immune homeostasis, as demonstrated in various autoimmune, infectious and inflammatory contexts. Yet, the impact of DCIR on cancer development remains largely unknown. Analysis of available transcriptomic data of colorectal cancer (CRC) patients revealed that high DCIR gene expression is associated with improved patients' survival, immunologically "hot" tumors and high immunologic constant of rejection, thus arguing for a protective and immunoregulatory role of DCIR in CRC. In line with these correlative data, we found that deficiency of DCIR1, the murine homologue of human DCIR, leads to the development of significantly larger tumors in an orthotopic murine model of CRC. This phenotype is accompanied by an altered phenotype of tumor-associated macrophages (TAMs) and a reduction in the percentage of activated effector CD4+ and CD8+ T cells in CRC tumors of DCIR1-deficient mice. Overall, our results show that DCIR promotes antitumor immunity in CRC, making it an attractive target for the future development of immunotherapies to fight the second deadliest cancer in the world.

The Role of C-Type Lectin Receptor Signaling in the Intestinal Microbiota-Inflammation-Cancer Axis

As a subset of pattern recognition receptors (PRRs), C-type lectin-like receptors (CLRs) are mainly expressed by myeloid cells as both transmembrane and soluble forms. CLRs recognize not only pathogen associated molecular patterns (PAMPs), but also damage-associated molecular patterns (DAMPs) to promote innate immune responses and affect adaptive immune responses. Upon engagement by PAMPs or DAMPs, CLR signaling initiates various biological activities in vivo, such as cytokine secretion and immune cell recruitment. Recently, several CLRs have been implicated as contributory to the pathogenesis of intestinal inflammation, which represents a prominent risk factor for colorectal cancer (CRC). CLRs function as an interface among microbiota, intestinal epithelial barrier and immune system, so we firstly discussed the relationship between dysbiosis caused by microbiota alteration and inflammatory bowel disease (IBD), then focused on the role of CLRs signaling in pathogenesis of IBD (including Mincle, Dectin-3, Dectin-1, DCIR, DC-SIGN, LOX-1 and their downstream CARD9). Given that CLRs mediate intricate inflammatory signals and inflammation plays a significant role in tumorigenesis, we finally highlight the specific effects of CLRs on CRC, especially colitis-associated cancer (CAC), hoping to open new horizons on pathogenesis and therapeutics of IBD and CAC.

THE VIABILITY OF LEUKOCYTES AND REACTIVE OXYGEN SPECIES GENERATION BY THEM IN RATS WITH CHRONIC COLITIS

OBJECTIVE

The aim: To assess reactive oxygen species production by leukocytes and their viability in rats with chronic colitis.

PATIENTS AND METHODS

Materials and methods: Reactive oxygen species production was estimated in leukocytes, isolated from rats with Dextran Sulfate Sodium-induced chronic colitis and control rats, by flow cytometry using the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate. Leukocyte viability and apoptosis stages were assessed by flow cytometry using annexin V and 7-aminoactinomycin D staining. White blood cell counting was carried out with using Hematology Analyzer.

RESULTS

Results: The increased fluorescence intensity of 2',7'-dichlorofluorescein in viable leukocytes by 36.7% was revealed in rats with chronic colitis compared control rats. A significant decrease in the percentage of viable cells and an increase in apoptotic cells were found compared to intact animals. Leukocytes, granulocytes, monocytes, lymphocytes counts in blood of experimental group animals were significantly higher compared to control those.

CONCLUSION

Conclusions: Our findings indicate that Dextran Sulfate Sodium-induced chronic colitis increases an intracellular production of reactive oxygen species by leukocytes. Despite of increased leukopoiesis it reduces viability of white blood cells and promotes their apoptosis via stimulation of oxidative stress.

Infection by Strongyloides venezuelensis attenuates chronic colitis induced by Dextran Sodium Sulfate ingestion in BALB/c mice

Inflammatory bowel diseases (IBD) are chronic health problems of difficult management and treatment. Epidemiological studies indicate an inverse association between helminth infections and IBD, and experimental data confirm that helminth infections modulate the severity of experimental acute colitis in mice. However, the effects of helminth infections on chronic colitis, which is clinically more relevant, have been poorly explored. Herein, we investigated whether Strongyloides venezuelensis infection in BALB/c mice can ameliorate chronic colitis induced by the ingestion of water containing 2.5% Dextran Sodium Sulfate (DSS) over three seven-day treatment cycles, with an interval of fourteen days between cycles. Infected-only, DSS-exposed-only, and non-exposed/uninfected experimental groups served as controls for comparing the severity of colitis and intestinal inflammation among different groups. Our data showed that S. venezuelensis infection in mice with DSS-induced chronic colitis reduced clinical signs, attenuated colon shortening and inflammation, and prevented mucus ablation. The modulatory effect was accompanied by a low concentration of IFN-γ, high concentrations of TGF-β, IL-22, and IL-33 in the colon, and a significant increase of the percentage of CD4+CD25+Foxp3+ Treg cells in the mesenteric lymph node (MLN). In conclusion, S. venezuelensis infection can reduce the severity of DSS-induced chronic colitis in mice possibly through the stimulation of Treg cells and modulatory cytokines, and induction of mucosal repair mechanisms.

Inhibition of Dextran Sodium Sulfate-Induced Experimental Colitis in Mice by Angelica Sinensis Polysaccharide

Studies have confirmed that Angelica sinensis, which is a famous medicinal food in China, can effectively alleviate the symptoms of ulcerative colitis (UC) in rats. However, as the major water-soluble ingredient, the specific effects of A. sinensis polysaccharide (ASP) on UC and potential mechanisms were uncertain. In this study, we aimed to elucidate the protective effects of ASP on dextran sulfate sodium (DSS)-induced UC and to further explore the mechanisms. ASP could significantly ameliorate the symptoms of weight loss, disease activity index score, and colon shortening caused by DSS. ASP treatment also significantly suppressed the myeloperoxidase activity in colon tissues. Furthermore, after ASP administration, the expression of the proinflammatory cytokines (interleukin [IL]-6, IL-1β, and tumor necrosis factor alpha) induced by DSS was remarkably suppressed, and there was a definite improvement in the expressions of tight junction proteins, such as zona occludens 1, occludin, and claudin-1. In addition, the results of apoptosis experiments showed that the apoptotic events were noticeably reduced after ASP treatment. Taken together, these results suggested that ASP may be a potential natural agent against UC.

Myeloid C-type lectin receptors in skin/mucoepithelial diseases and tumors

Myeloid C‐type lectin receptors (CLRs), which consist of an extracellular carbohydrate recognition domain and intracellular signal transducing motif such as the immunoreceptor tyrosine‐based activation motif (ITAM) or immunoreceptor tyrosine‐based inhibitory motif (ITIM), are innate immune receptors primarily expressed on myeloid lineage cells such as dendritic cells (DCs) and Mϕs. CLRs play important roles in host defense against infection by fungi and bacteria by recognizing specific carbohydrate components of these pathogens. However, these immune receptors also make important contributions to immune homeostasis of mucosa and skin in mammals by recognizing components of microbiota, as well as by recognizing self‐components such as alarmins from dead cells and noncanonical non‐carbohydrate ligands. CLR deficiency not only induces hypersensitivity to infection, but also causes dysregulation of muco‐cutaneous immune homeostasis, resulting in the development of allergy, inflammation, autoimmunity, and tumors. In this review, we introduce recent discoveries regarding the roles of myeloid CLRs in the immune system exposed to the environment, and discuss the roles of these lectin receptors in the development of colitis, asthma, psoriasis, atopic dermatitis, and cancer. Although some CLRs are suggested to be involved in the development of these diseases, the function of CLRs and their ligands still largely remain to be elucidated.

A Role of Exopolysaccharide Produced by Streptococcus thermophilus in the Intestinal Inflammation and Mucosal Barrier in Caco-2 Monolayer and Dextran Sulphate Sodium-Induced Experimental Murine Colitis

Exopolysaccharide (EPS) produced by probiotics may play an important role in gastrointestinal disease prevention, including ulcerative colitis. However, there is no literature reporting on the intervention effects of purified EPS. The aim of this study was to investigate the alleviating effect of the purified EPS produced by Streptococcus thermophilus MN-BM-A01 on murine model of colitis induced by dextran sulphate sodium (DSS). A water-soluble heteropolysaccharide (EPS-1) isolated from MN-BM-A01 was composed of rhamnose, glucose, galactose, and mannose in a molar ratio of 12.9:26.0:60.9:0.25, with molecular weight of 4.23 × 10⁵ Da. After EPS-1 administration, the disease severity of mouse colitis was significantly alleviated, mainly manifesting as the decrease of disease activity index and mitigated colonic epithelial cell injury. Meanwhile, pro-inflammatory cytokines levels (tumor necrosis factor-α, interleukin-6, and interferon-γ) were significantly suppressed, the reduced expressions of tight junction protein (claudin-1, occludin, and E-canherin) were counteracted. In addition, the results in vitro showed that EPS-1 protected intestinal barrier integrity from the disruption by lipopolysaccharide in Caco-2 monolayer, increased expression of tight junction and alleviated pro-inflammatory response. Collectively, our study confirmed the protective effects of purified EPS produced by Streptococcus thermophilus on acute colitis via alleviating intestinal inflammation and improving mucosal barrier function.

Co-Stimulation-Impaired Bone Marrow-Derived Dendritic Cells Prevent Dextran Sodium Sulfate-Induced Colitis in Mice

Dendritic cells (DC) are important in the onset and severity of inflammatory bowel disease (IBD). Tolerogenic DC induce T-cells to become therapeutic Foxp3+ regulatory T-cells (Tregs). We therefore asked if experimental IBD could be prevented by administration of bone marrow-derived DC generated under conventional GM-CSF/IL-4 conditions but in the presence of a mixture of antisense DNA oligonucleotides targeting the primary transcripts of CD40, CD80, and CD86. These cell products (which we call AS-ODN BM-DC) have demonstrated tolerogenic activity in preventing type 1 diabetes and preserving beta cell mass in new-onset type 1 diabetes in the NOD mouse strain, in earlier studies. In addition to measuring efficacy in prevention of experimental IBD, we also sought to identify possible mechanism(s) of action. Weight, behavior, stool frequency, and character were observed daily for 7–10 days in experimental colitis in mice exposed to dextran sodium sulfate (DSS) following injection of the AS-ODN BM-DC. After euthanasia, the colons were processed for histology while spleen and mesenteric lymph nodes (MLNs) were made into single cells to measure Foxp3+ Treg as well as IL-10+ regulatory B-cell (Breg) population frequency by flow cytometry. AS-ODN BM-DC prevented DSS-induced colitis development. Recipients of these cells exhibited significant increases in Foxp3+ Treg and IL-10+ Breg in MLN and spleen. Histological examination of colon sections of colitis-free mice remained largely architecturally physiologic and mostly free of leukocyte infiltration when compared with DSS-treated animals. Although DSS colitis is mainly an innate immunity-driven condition, our study adds to the growing body of evidence showing that Foxp3+ Treg and IL-10 Bregs can suppress a mainly innate-driven inflammation. The already-established safety of human DC generated from monocytic progenitors in the presence of the mixture of antisense DNA targeting the primary transcripts of CD40, CD80, and CD86 in humans offers the potential to adapt them for clinical IBD therapy.

Rheumatoid arthritis: identifying and characterising polymorphisms using rat models

Rheumatoid arthritis is a chronic inflammatory joint disorder characterised by erosive inflammation of the articular cartilage and by destruction of the synovial joints. It is regulated by both genetic and environmental factors, and, currently, there is no preventative treatment or cure for this disease. Genome-wide association studies have identified ∼100 new loci associated with rheumatoid arthritis, in addition to the already known locus within the major histocompatibility complex II region. However, together, these loci account for only a modest fraction of the genetic variance associated with this disease and very little is known about the pathogenic roles of most of the risk loci identified. Here, we discuss how rat models of rheumatoid arthritis are being used to detect quantitative trait loci that regulate different arthritic traits by genetic linkage analysis and to positionally clone the underlying causative genes using congenic strains. By isolating specific loci on a fixed genetic background, congenic strains overcome the challenges of genetic heterogeneity and environmental interactions associated with human studies. Most importantly, congenic strains allow functional experimental studies be performed to investigate the pathological consequences of natural genetic polymorphisms, as illustrated by the discovery of several major disease genes that contribute to arthritis in rats. We discuss how these advances have provided new biological insights into arthritis in humans.

Absence of DCIR1 reduces the mortality rate of endotoxemic hepatitis in mice

Dendritic cell immunoreceptor (DCIR) is a C-type lectin with an immunoreceptor tyrosine-based inhibitory motif (ITIM). Mice lacking DCIR1 (Dcir1^-/- mice) show higher susceptibility to chronic arthritis with increasing age, suggesting that DCIR1 is involved in immune modulation via its ITIM. However, the role of DCIR1 in acute immune responses is not clear. In this study, we explored its role in acute experimental hepatitis. Upon injection of d-galactosamine and lipopolysaccharide, Dcir1^-/- mice showed decreased mortality rates and serum levels of alanine aminotransferase. In early onset hepatitis, serum levels of TNF-α, which primarily cause inflammation and hepatocyte apoptosis, were significantly lower in Dcir1^-/- mice than in WT mice. In the liver of Dcir1^-/- mice, influx of neutrophils and other leukocytes decreased. Consistently, the levels of neutrophil-chemoattractant chemokine CXCL1/KC, but not CXCL2/MIP-2, were lower in Dcir1^-/- mice than in WT mice. However, chemotaxis of Dcir1^-/- neutrophils to CXCL1/KC appeared normal. Pervanadate treatment induced binding of DCIR1 and Src homology region 2 domain-containing phosphatase (SHP)-2, possibly leading to CXCL1/KC expression. These results suggest that DCIR1 is involved in exacerbation of endotoxemic hepatitis, providing a new therapeutic target for lethal hepatitis.